The present invention relates to the evaluation of affective brain function and, more particularly, to the monitoring of such function as an indication of the reception of visual stimulus.
The human response to visual stimulation involves a complex system of physiological and neurological systems. In the field of advertising and website design, as well as other fields where emotional responses to visual stimulus are as important than cognitive responses, there is a desire to measure the former and distinguish between the two using objective criteria.
It has long been recognized that certain physiological responses, such as pupillary changes, are associated with cognitive activity (Ahern, S. and Beatty, J. (1979) Science 205: 1289-1292). Monitoring of such changes is considered important in analyzing the usefulness of a visual display and its effectiveness in providing an efficient roadmap to desired information. For example, U.S. Pat. No. 6,090,051 describes a method of analyzing cognitive activity as a function of mathematically normalized pupillary responses to visual stimuli, such as viewing webpages. These methods are important to the analysis of cognitive analytical functions, such as arithmetics, sentence functioning and language skills, but are not as closely correlated to the analysis of affective neurological functions, such as the likeability of a particular visual stimulus or the aversive impact of a disagreeable stimulus.
Pupil dilation is primarily the result of the integrated activity of two groups of muscles located on the iris. One set of muscles (the circular muscles) encircles the pupil: when activated, this set of muscles serves to constrict the diameter of the pupil and make it smaller. The second set of muscles (the radial muscles) lies immediately outside the circular muscles and extends radially from the pupil out through the iris. When activated, the radial muscles pull the pupil diameter outward and cause it to become larger. These two sets of muscles typically work together through reciprocal innervation, a physiological process involving both agonistic and antagonistic responses. The result of this process is a response larger than either set of muscles alone could produce.
When stimulated by light, the pupil responds by oscillating its size. Insofar as this response results in changes in pupil diameter, this response has been extensively studied. During the light reflex, the circular muscles act as the agonist and are stimulated to contract, while the radial muscles act as the antagonists and are inhibited from dilating the pupil. The reflex is fleeting, and can be measured as a pulsing of the pupil (Lowenfield, in xe2x80x9cThe Pupil: Anatomy, Physiology and Clinical Applications, Vol. I; Ames, Iowa, Iowa State University Press.)
When an individual""s pupillary response to visual stimulus is measured as a way of assessing the effectiveness of visual input requiring cognitive processing, the pupillary response is recorded and processed in a manner that allows one to distinguish it from a simple light response as described in U.S. Pat. No. 6,090,051. Such measurements, and post-processing thereof, are specifically designed to analyze xe2x80x9ctasksxe2x80x9d associated with effortful cognitive processing. These methods are distinct from other related methods that are designed to do the opposite, i.e. correlate measured eye movements to assumed cognitive activity as described in U.S. Pat. No. 6,102,870. In other words, whereas the ""051 patent describes methods to evaluate cognitive activity, i.e. thought processes, in response to visual stimulus, the ""870 patent describes methods to correlate visual responses to thought processes, i.e. xe2x80x9cmental statesxe2x80x9d, which are predetermined to be associated with such responses. Accordingly, the ""051 patent focuses prospectively on designing ways to alter visual stimulus to optimize the cognitive response, while the ""870 patent focuses retrospectively on characterizing visual effects as being indicative of predetermined mental states.
In comparison to such methods that are specifically designed to evaluate cognitive workload, the present patent application provides methods for, inter alia, evaluating affective, or emotional, non-cognitive responses to visual stimulus. The cognitive response is perhaps more important in fields such as training videos, visual learning methods and other such xe2x80x9cthinkingxe2x80x9d tasks, the non-cognitive response may be more important in fields such as television and computer advertising, and the computer game industry, the commercial success of which is most influenced by immediate emotional responses to visual stimulus.
It has long been recognized that the brain is highly lateralized, in that the two halves of the brain are not exactly alike. In fact, both sides of the brain, or xe2x80x9chemispheresxe2x80x9d, have certain functional specializations that appear to be localized in one-half of the brain. As far back as the 1800s, Paul Broca, a French neurosurgeon, suggested that the left hemisphere was associated with an analytical skill such as language. Since then, many other investigators have determined that there is a relationship between xe2x80x9chandednessxe2x80x9d (i.e. an individual writes primarily with their right or left hand) and brain hemisphere function.
There is a wide body of scientific literature that describes that, in general, the left brain hemisphere is associated more with linear, logical, analytical, and unemotional thinking, whereas the right brain is associated more with spatial, creative, emotional and intuitive thinking. Although such generalizations are still not fully understood at a neurophysiological level, this literature and the studies associated therewith provide impetus for the design of systems to measure physical responses to visual stimulus that are selectively associated more with a xe2x80x9cright brainxe2x80x9d response than a xe2x80x9cleft brainxe2x80x9d response.
More specifically, the present invention describes the unexpected discovery that the abrupt pupillary changes that were, in part, previously attributed to xe2x80x9cnoisexe2x80x9d during the measurement of pupillary responses are actually meaningful and extremely useful measurements of affective brain responses.